Soft hammering head



March 15, 1955 M. B. MITTLEMAN 2,704,094

SOFT HAMMERING HEAD Filed May 5, 1952 37 III 14 III" I INVENTO Rhypo/v.8. Mm [AM/v ATTORNEY United States Patent SOFT HAMMERING HEADMyron Budd Mittleman, Larchmont, N. Y.

Application May 5, 1952, Serial No. 286,193

7 Claims. (Cl. 145-36) The present invention relates to soft hammeringheads adaptable for use in hammers, drifts and the like and moreparticularly to improvements in such heads of the type having a hollowportion or chamber therein.

As distinguished from hard hammers, soft hammers are softer than thework on which they are employed. They are commonly used to form softmetals, drive or knock apart close-fitting parts and, in general,wherever it is desired to strike a work piece without leaving a mark orchanging its dimensions significantly. Matenals sometimes employed forsoft hammering heads include wood, rubber, rawhide, plastic, lead andcopper alloys. Sometimes they are referred to as safety hammers, adescription which stems from their non-ferrous content and hence theirsafety in explosive atmospheres where steel hammers might strike aspark.

Non-metallic heads generally require fairly large bulk for a givenweight and, depending upon the material and work are subject tosplintering, ripping, shredding, fracturing and mushrooming. Usuallythey have relatively short lives even for soft hammering heads which, asa class, are considered expendable tools. On the other hand, metallicheads, while of relatively longer usefulness are particularly subject tomushrooming about the striking face. Continued use after mushroomingcauses a chipping of the upturned edges and hence ahigh rate ofindustrial accident.

In an attempt to minimize the peripheral upsetting of such strikingfaces, Gallant (U. S. Patent No. 2,355,641) described the use of aninterior chamber or hollowed portion within the hammering head, but hespecified that the front wall thickness between the chamber and strikingsurface should be thicker than the side Walls and failed to makeadequate provision to control the plastic flow of the metal comprisingthe head, with the result that heads made in accordance with Gallantsdescriptions are still quite substantially subject to mushrooming and,relative to heads made in accordance with the present invention areunnecessarily short-lived.

An object of the present invention is to provide a soft hammering headconstructed to minimize the likelihood of mushrooming about the strikingsurface.

A further object is the provision of such a head of longer usefulnessthan previously known soft hammers.

These and other objects are achieved, in a preferred form, by ahammering head of a soft material (such as copper or copper alloyed witha small amount of tin or zinc, depending upon the hardness required)which tapers generally from the eye or portions removed from the eyetowards the striking surface, having a hollow chamber within the head,the front wall of said head, lying between the forward boundary of saidchamber and the striking surface being of less thickness than the sidewalls bounding said chamber. A pair of opposite side walls may haveundulating interior surfaces, preferably of serriform section. As anadditional element to control the plastic flow of the metal, thejunction of the unserrated interior side walls and the interior of thefront or striking wall may be an oblique wedge shaped section.

Other objects and a fuller understanding of the present invention may behad by referring to the following description and claims, taken inconjunction with the accompanying drawing which illustrates preferredembodiments thereof, it being understood that the foregoing statement ofobjects of the invention and the brief summary thereof are intended togenerally explain the same without limiting it in any manner.

2,704,094 Patented Mar. 15, 1955 Fig. 1 is a side elevation of a headfor a soft hammer embodying the present invention, the handle thereforbeing shown in dashed outline.

Fig. 2 is a sectional view of the said elevation taken midway throughthe head.

Fig. 3 is the same sectional view as Fig. 2 but taken after the head hasbeen pounded and at a point where it approaches the end of its use.

Fig. 4 is a section in elevation of the hammer of Fig. 1 but taken alongline 4 of Fig. 2.

Fig. 5 is a similar section but taken along line 5 in Fig. 4 (of thepounded hammer).

Fig.6 is a horizontal section of the hammer shown in Fig. 1 but takenalong line 6--6 of Fig. 4.

Fig. 7 is an elevational view of a drift employing a hammering headembodying the present invention, portions thereof being cut away toreveal the inner construction.

Referring to the drawing, and more particularly to the embodiment of theinvention as shown in Figs. 1 through 6, it comprises a soft hammeringhead preferably of a copper alloy which generally tapers towards the endor striking surfaces 10 and 11 having substantially normal surfacecenter panels 12, 13, 14 and 15, and tapering surface end panels 16, 17,18 and 19 in the lower half of the head (as shown in the drawings) and20, 21, 22, 23 in the upper half of said head, the junctions of thecenter panels, the junctions of the side panels and the junctions of theterminal portions of the side panels with the striking faces beingbevelled. An eye 24, adapted to receive a hammer handle 25 extendstransversely through center panels 13 and 16, said handle being securedto said head by a pin 26 placed in the bore 27 extending through panels12 and 14 as well as handle 25. The junction of panel 15 with the upperand lower surfaces of eye 24 are bevelled to form oblique surfaces 28and 29.

Internally, the head contains lower and upper chambers 30 and 31, incommunication with eye 24 (to permit easy casting), said chambers beingroughly oblong in vertical sections parallel to the center panels, theinterior of the opposed side walls 32 and 33 of lower chamber 30, beingthe walls extending from said chamber to panels 12 and 16 on one sideand 14 and 18 in the other respectively, having substantially planarinterior surfaces substantially parallel with center panels 12 and 14respectively, while the remaining opposed side walls 34 and 35 of lowerchamber 30 are undulating, having indented portions 34a, 34b, and 340and 35a, 35b and 350 respecnvely leaving inwardly extending ridges 34dand 34e and 3511 and 35e, respectively, forming walls of serriformoutline. At the junction of side walls 32 and 33 and front (or striking)wall 36 of chamber 30 are oblique surfaces 37 and 38 substantiallyparallel to the faces of the bevels at the junctions of end panels 16and 18 with striking surface 10. The undulations or serrations areformed 1n said side walls to lend structural strength to the walls andat the same time assist in the control of tle plastic flow of the metalof the head under conditions 0 use.

Since chamber 31 is constructed identically with chamber 30, primes areemployed to designate the correspondlng elements.

The head is made by a conventional casting process. Handle 25 is theninserted in eye 24, and pin 26 is passed through bores 27 in the headand handle to complete the assembly.

After the hammer has been used, the changes observable 1n Figs. 3 and 5take place. Generally, the hammer becomes shorter longitudinally andbroader transversely. S1m1larly chambers 30 and 31 become shorterlongitudinally and broader transversely. There is no falling in of themetal laterally upon the undulating side walls, but on the contrary anoutward flow. Since when both striking surfaces of the hammer are usedeach half transforms symmetrically, it will suffice to note the changesin the lower half.

Front or striking wall 36 becomes somewhat thicker longitudinally andsubstantially wider laterally. Oblique surfaces 37 and 38 disappear,striking wall 36 having pushed up upon them. Side walls 34 and 35 becomethicker, more so near striking wall 36 than near eye 24.

The distance between indentations 34a and 35a in side walls 34 and 35increase substantially and the interior surfaces of the portions of saidwalls between said indentations and the interior surface of the strikingwall bow inwards. The corresponding lateral distances between ridges 34dand 35d, between indentations 34b and 35b, between ridges 34c and 35sand between indentations 34c and 35c likewise increase, but the extentof such widening decreases as eye 24 is approached. End panels 17 and 19depart slightly from their original linear surface and appear somewhatconvex longitudinally.

The plastic flow of the metal is such that eye 24 narrows and compresseshandle 25, binding it tighter with use. Oblique surfaces 28 and 29 areeffective to prevent the longitudinally-inwardly pressed metal about thelateral periphery of the eye at said surfaces from biting into thewooden handle, and causing the same to be snapped off. On the otherlateral periphery of said eye, at panel 13, the outward travel of themetal is such as to cause a slight but noticeable bow, giving panel 13,which was originally planar, a concave surface.

Side walls 32 and 33 (those with the inner planar surfaces) thicken,more greatly near striking wall 36 and less so proximate bore 27.Striking surface 10, when laterally viewed as in Fig. 5, appears convex,the metal about the edges having travelled further toward bore 27 thanthat in the middle portion. The inner surface of striking wall 36 iscorrespondingly changed in shape and appears concave. It is believedthat the buttressing effect of the wedge shaped junctions of side walls16 and 18 with the inner surface of striking wall 36, presenting obliquesurfaces 37 and 38 causes this resulting convexity of the strikingsurface by angularly channelling metal flow outwardly and upwardly.

The thickening or outward movement of side walls 32 and 33 causes pin 26to appear countersunk in panels 12 and 14.

Significantly, there is no mushrooming at the striking surface and thehead retains generally its tapered outline throughout its useful life.By reason of the improved means of channelling the plastic fiow of themetal, while it of course is subject to a forging efiect, i. e., ahardening at the striking surface with use, it is superior to knownhammers in that it takes a great deal of use to harden it to the pointof hardness which other hammers reach with much less use.

It is critical to the success of the hammer described that striking wall36 be narrower than the side walls.

To understand why, it is necessary to analyze what happens upon impactwith a work piece and shortly thereafter.

'Take first, the case of a solid copper-alloy hammer. Assume it iscomposed of discrete particles which are held together by cohesiveforces but which particles are nevertheless loosely packed so that thehammer may be compressed. The hammer is swung so that it will hit aplanar work piece normally thereto. As the hammer is moved, eachconstituent particle is given a certain momentum and at the instantpreceding impact all are travelling at the same velocity. At the momentof impact, each particle tends, in accordance with Newtons first law ofmotion, to continue in a straight line, e. g. normal to the worksurface. Ignoring for the moment the cohesive forces at work in thehammer head and the shapes of the particles, each particle is drivenforward into contact with its forward neighbor, except the terminalparticles in the striking surface which strike the harder surface of theWork piece and may be deemed relatively to stand still. The distanceeach particle travels will then be a function of its distance from thestriking surface and the elasticity of the-particles. The force exertedupon the terminal particles would be a function of the momentum of theindiivdual particles lying rearward of the striking surface.

However, the particles are not sheets, having irregular surfaces andtherefore upon collision with forward neighbors some would be deflected.Hence there are lateral components of movement and force upon thecollisions. Manifestly, these are much smaller than the longitudinalmovements and forces. Hence while most of the metal moves downward onimpact some of it is caused to move laterally. If a lateral slice acrossthe hammer head is considered, then the more mass in such slice, thegreater the lateral component. When the hammer is solid, assuminginitially upon impact the lateral forces are equally distributed, sinceit is easier for the particles to move outward toward the lateralsurfaces of the slice than inwardly to compact the slice, more metalwill move laterally outwardly than laterally inwardly. It may beconcluded then, that the more mass there is in a horizontal slice of thehammer, the more the slice will grow laterally on impact. Of course,after impact, the elasticity of the hammer head operates to tend torestore it to its original shape, but it does not quite do so, therebeing some residual displacement (plastic fiow). Since the greatestforce is exerted upon the terminal layer, that is where mushroomingtakes place.

In accordance with the above, it is then wise to have a chambered hammerhead since then the number of particles which may flow against thestriking surface directly, upon impact is minimized. Of course, thecohesive forces at work in the head cause the greater portion of themomentum of the particles to be transmitted to the striking surface, butthey are then applied in such a way that lateral particle flow in theterminal layer is minimized. But doubly important is the correlativeconclusion that the thinner the striking wall the less the laterallyoutward travel at this most critical area, and hence the minimization ofthe tendency to mushroom.

Confirmation of the validity of the lateral slice" analysis is found inthe fact that walls 34 and do not collapse toward each other upon use ofthe hammer, but actually move apart. Each of said walls are connected atboth ends to solid walls 32 and 33 which act as would the solid hammerfirst posited. The expansion of these solid walls in accordance with theprinciples outlined above causes them to carry the serrated walls awayfrom each other.

To give strength to walls 34 and 35 they were given the serriformsection shown. To maintain the dimentional or structural stability ofthe hammer it is necessary that the side walls be thicker than thestriking surface, the thickness of which has been kept to a minimum inaccordance with the principles developed above.

Another confirmation of the lateral slice approach may be observed inthe flow about handle 25, there being the lessening of lateral flowimmediately proximate the handle due to the fact that flow is easieragainst the soft wood handle than against metal causing the concavity inpanel 13. Similarly, the other displacements upon use may be similarlyemployed to support the analysis. Then, too, when only one side of thehead is pounded, metal flows from the unpounded portion adjoining eye 24into the eye and against the wood of handle 25 and also slightlylaterally to similarly form the type of concavity mentioned above.

Another embodiment of the present invention is shown in Fig. 7 whichillustrates a drift incorporating a hammering head 39 similar in allrespects to the one previously described except that it has lessserrations and the handle, in this instance preferably brass handle 40,is longitudinally axially associated with the head being secured theretoby a pin 41 passing through aligned bores 42 in said head and handle. Awasher 43 acts to seat handle on head 39. For better gripping a rubbersleeve 44 is placed about said handle and held in place by an upperwasher 45 riveted to the top of handle 40. Said upper washer also actsas a detent for the users hand.

Although the subject invention has been described with a certain degreeof particularity, it is understood that the present disclosure has beenmade only by way of example and that numerous additional changes in thedetails of construction, combination and arrangement may be resorted towithout transcending the scope of the invention as hereinafter claimed.

What is claimed is:

l. A soft hammering head formed of a relatively soft plasticallydeformable material, including a body, having a chamber formed therein,said chamber being defined by side walls and a front striking wall, thethickness of said side walls proximate the junction with said frontstriking wall being greater than the thickness of said front strikingwall. lower portions of said side walls tapering toward said strikingwall.

A soft hammering head as described in claim 1, a

pair of opposing side walls having inner undulating surfaces.

3. A soft hammering head as described in claim 2, said undulatingsurfaces being serriform in section.

4. A soft hammering head as described in claim 3, the portions of saidside walls of serriform section proximate the junctions with saidstriking wall sloping initially outwardly from said striking wall.

A soft hammering head as described in claim 1, a pair of opposing wallshaving substantially planar surfaces, such side walls and said strikingwall meeting at a solid oblique corner.

6. A soft hammer head having a body of greater longitudinal than lateralextent and having a centrally laterally extending eye therethroughadapted to receive a handle, and having two chambers formed therein oneon either side of said eye, each of said chambers being defined by sidewalls and terminal striking walls, the thickness of said side wallsproximate the junction with said front striking wall being greater thanthe thickness of said striking walls, exterior portions of said sidewalls proximate said striking wall tapering toward said striking walls,

a pair of opposing side walls in each such chamber having innerundulating surfaces.

7. A soft hammering head for a drift formed of a relatively softplastically deformable material having an axial cavity formed therein,the upper portion of the said cavity comprising an eye adapted toreceive a handle and the lower portion thereof being laterally definedby side walls and terminally defined by a front striking wall, saidstriking wall being thinner than the thickness of said side wallsproximate the junction with said front striking wall, said side wallshaving inner undulating surfaces, exterior portions of said side wallsproximate said striking wall tapering inwardly toward said strikingwall.

References Cited in the file of this patent UNITED STATES PATENTS2,355,641 Gallant Aug. 15, 1944 20 2,566,517 Dicks Sept. 4, 19512,607,379 Piampiano et a1 Aug. 19, 1952

